This invention relates generally to cutting apparatus and more particularly to ultra high pressure abrasive waterjet cutting apparatus for cutting nuclear reactor structural components.
Structural components within nuclear reactor pressure vessels (RPV) become irradiated, and those components nearest the reactor core become highly irradiated. When such structural components require removal from the RPV and replacement, the components must be unbolted or cut from their original position and then subsequently cut into smaller sections for shipping and final storage. Because these components are radioactive, they must remain underwater to provide radiation shielding to workers in the proximity of the reactor components. The cutting process used to cut these structural components into smaller sections must therefore be performed underwater.
Known cutting apparatus for cutting reactor internals typically include a gantry type bridge with a partially submersible mast/manipulator attached. The gantry bridge and submersible manipulator permits from three to five axis of motion for the cutting nozzle. The disadvantages of these known cutting apparatus are that the gantry type bridge needs to be mounted on existing rails in the reactor, or new rails have to be installed. Because the cutting apparatus is mounted above the reactor internal components, it interferes with overhead crane cables when the crane is used for handling cut pieces of the reactor internal components. Additionally, the cutting apparatus interferes with the service platform which is used by personnel over the cutting area for manipulating rigging and cameras. Additionally, there is a possibility of the gantry running over hoses and power cables. It is also known that the mast/manipulator has stability problems when used with an ultra high pressure waterjet nozzle because of the force applied by the reaction to the ultra high pressure waterjet.
It would be desirable to provide a cutting apparatus for cutting reactor internal component parts in a nuclear reactor that does not include a gantry type bridge mounted on rails above the reactor.
In an exemplary embodiment, an ultra high pressure abrasive waterjet cutting apparatus for underwater cutting of structural components of a nuclear reactor includes a multi-axis manipulator, an ultra high pressure abrasive water jet (UHP) cutting nozzle coupled to the manipulator, a collection stand assembly, and a collection hood movably coupled to the collection stand assembly. The multi-axis manipulator is configured to mount on the floor of the pool of water in which the structural component is positioned for cutting.
The multi-axis manipulator includes a base actuator configured to mount on the pool floor, a vertical actuator movably coupled to the base actuator. The vertical actuator extends substantially perpendicular to the base actuator and is movable along the longitudinal axis of the base actuator. A horizontal actuator is movably coupled to the vertical actuator. The horizontal actuator extends substantially perpendicular to the vertical actuator and is movable along the longitudinal axis of the vertical actuator. The horizontal actuator is also movable along the longitudinal axis of the horizontal actuator. A rotating manipulator is coupled to one end of the horizontal actuator, and the UHP cutting nozzle is coupled to the rotating manipulator. The UHP cutting nozzle is movable in an arc around the end of the horizontal actuator.
The collection stand assembly includes a vertical support stand configured to mount on the pool floor or the pool wall. A support frame is movably coupled to the support stand with the support frame movable along the longitudinal axis of the support stand. At least one positioning cylinder is coupled at one end to the support frame and at an opposite end to the collection hood.
The UHP cutting apparatus can further include a turntable configured to support the component to be cut and to move the component in relation to the UHP cutting nozzle and the collection hood. The turntable includes a non-movable center portion and a movable outer portion. The multi-axis manipulator is mounted on the non-movable center portion of the turntable.
To cut a structural component of a nuclear reactor, for example a shroud, utilizing the ultra high pressure abrasive waterjet cutting apparatus described above, the cutting apparatus and shroud are positioned in a pool of water, for example the reactor containment pool. Particularly the multi-axis manipulator is mounted on the floor of the pool on one side of the shroud, for example the interior of the shroud, and the collection stand assembly is mounted in the pool on the opposite side of the shroud, for example, the outside of the shroud, and in alignment with the cutting nozzle coupled to the manipulator.
The collection stand assembly support frame is moved along the vertical support stand to position the collection hood in alignment with the desired cutting area. The collection hood positioning cylinders are activated to position the collection hood adjacent the outer surface of the shroud.
The base and vertical actuators are activated to position the cutting nozzle at the starting point of the cut. The horizontal actuator is actuated to position the cutting nozzle adjacent the inner surface of the shroud. To make a horizontal cut, the cutting nozzle is actuated and the base actuator moves the vertical actuator, and thus the cutting nozzle, in a horizontal direction. The abrasive containing UHP water jet cuts through the shroud and enters the collection hood positioned on the opposite side of the shroud The water filtration system connected to the collection chamber outlet port filters the used abrasive and kerf material from the water before it is returned to the reactor To make a vertical cut the vertical actuator moves the horizontal actuator, and thus the cutting nozzle in a vertical direction. To cut parts that extend from the inner surface of the shroud, the rotating manipulator moves the cutting nozzle in an arc.
The above described ultra high pressure abrasive waterjet cutting apparatus is supported by the floor of the pool, thus eliminating the need for a gantry type bridge and partially submersed mast/manipulator. The above described cutting apparatus does not interfere with overhead crane cables when the crane is used for handling cut pieces of the reactor internal components, or interfere with the service platform which is used by personnel over the cutting area for manipulating rigging and cameras.